In recent years, a power device that has a high breakdown voltage characteristic and is used to allow a large current to flow has been actively developed. In the development of such a power device, a nitride semiconductor that is made of a material, which has a high insulation breakdown electric field and a high saturation electron velocity, has attracted attention. The power device using a GaN (gallium nitride)-based semiconductor among the nitride semiconductors, as disclosed in NPL 1 and NPL 2, has been expected to greatly contribute to energy saving in future low-loss and high-speed power switching systems.
However, in the production of a GaN power device, when blade dicing, which is normally used for dicing the silicon semiconductor wafer, is performed, since a GaN film is hard, it is difficult to separate the semiconductor wafer successfully. In addition, due to the difference in lattice constants and thermal expansion coefficients between a silicon substrate and the GaN film, in the semiconductor wafer, a large amount of stress occurs in the vicinity of the interface between the silicon-based substrate and the GaN film. In this state, when the mechanical impact of the dicing is applied to the vicinity of the interface, there is a problem that a crack or the like starts from the vicinity of the interface. Therefore, in the production of the GaN power device, laser dicing is used in many cases.